Well if you already have funds to park then there are many ways but if you want a real stable source where you don’t have to invest any capital.
The only way is to Learn a skill and sell it. Be it programming, affiliate marketing, blogs or whatever stuff you are interested in.
I have started my online money making journey 5 years ago after 6 months of learning to program through online blogs it’s paying off well.
I have never had a job and has been all in into freelancing since start of my career, I feel I am at-least lean FIRE now.